Rubber composition and method of preserving rubber



Patented Get. 9, 1934 UNITED STATES PA Y RUBBER COMPOSETION AND METHOD OF PRESERVING RUBBER Arthur W. Sloan, Akron, Ohio, assignor to The B. F. Goodrich Company, New York, N. Y., a corporation of New York No Drawing. Original application March 7, 1931,

Serial No. 521,010. Divided and this application February 9, 1933, Serial No. 656,031

20 Claims.

This invention relates to the art of rubber manufacture, and particularly to the preparation of rubber compositions which resist the deterioration due to aging or to exposure to the atmosphere. It has long been known that such deterioration can be greatly retarded by treating the rubber either before or after vulcanization with certain substances known as age-resisters or anti-oxidants. The chief object of this invention, then, is to provide a new and superior class of anti-oxidants for rubber.

The substances which are employed as antioxidants according to this invention are secondary amino derivatives of hydrocarbons containing two or more aromatic ring structures attached to a central aliphatic nucleus, These compounds may, if desired, contain other basic or neutral substituents including the radicals of ethers, alcohols, primary and tertiary amines, etc., but strongly acidic substituent groups such as carboxyl or sulphonic acid groups which have the effect of greatly retarding vulcanization, and other groups containing doubly bound oxygen, nitrogen, sulphur, or other inorganic elements, should in general be avoided because of their reduced or even negative anti-oxidant power or because of their undesirably strong effect on the vulcanization of the rubber.

For example, the following substances are typical members of the class of substances outlined above: p-phenylamino tetraphenyl methane, tolyl p-amino tetraphenylmethane, naphthyl pamino tetraphenylmethane, p-biphenyl p-amino tetraphenylmethane, p-phenylamino phenyl tritolyl methane, p-phenylamino phenyl tri-biphenyl methane, biphenyl-amino tetra-biphenyl methane, p-phenylamino phenyl trianisyl methane, p-phenylamino phenyl trinaphthyl methane, p-naphthylamino phenyl trina'phthyl methane, p-benzylamino tetraphenylmethane, p-isopropylamino tetraphenylmethane, diphenyl p, p diamino diphenyl dimethyl methane, triphenyl triamino triphenyl methane, diphenyl diamino diphenyl carbincl, p-phenylamino p dimethylamino diphenylmethane, p-phenylamino p amino diphenylmethane, dinaphthyl diamino diphenylmethane, mononaphthyl diamino diphenylmethane, diphenyl diamino diphenylmethane, diphenyl diamino triphenylmethane, dibenzyl diamino diphenyl methane, diethyl diamino diphenyl methane, p, p di-triphenylmethyl diphenyl ethylene diamine, diphenyl p, p diamino dibenzyl, p-triphenylmethyl p'phenylamino diphenylamine, p-phenylamino phenyl xylyl methane, triphenylmethyl p-amino tetraphenylmethane, etc.

The compounds enumerated above are readily prepared from inexpensive raw materials by the usual reactions familiar to organic chemists. For example, the diaryl diamino diphenyl methane compounds are readily prepared by condensing aniline hydrochloride first with formaldehyde and then with a phenol or an aromatic amine. The secondary amino tetra-aryl methane compounds are most readily prepared by condensing a triaryl methyl chloride with a diarylamine; although the primary amine may be prepared first, if desired, by reacting the triaryl methyl chloride with aniline hydrochloride, the product being then further reacted with a phenol or amine to give the desired secondary amine.

Any one or a mixture of several of the aboveenumerated substances or of these substances with other known anti-oxidants may be incorporated into rubber with good effect on its ageresisting properties. For example from to 5% of such an anti-oxidant may be mixed with the rubber before vulcanization, the anti-oxidant having substantially no accelerating effect and therefore ordinarily not necessitating an adjustment of vulcanizing conditions. Alternately, the anti-oxidant may be applied to the surface of crude or vulcanized rubber, say in the form of a powder, paste, or solution. Rubber so treated resists the deteriorating influence of age and exposure to the elements far better than similar untreated rubber.

Example 1.-As a specific example of one embodiment of the method of this invention, a typical the tread composition was prepared containing: blended plantation rubbers approximately 100 parts by weight, sulfur 5.5 parts, zinc oxide 30 parts, gas black l0 parts, mineral rubber 10 parts, palm oil 5 parts, and hexamethylene tetramine 0.75 part. This was divided into portions, one of which was used as a control. To each of the others was added 0.95 part (0.5% of the weight of the composition) of one of the abovedescribed anti-oxidants. The compositions were thoroughly mixed, and. vulcanized in a press for 45 minutes at 145 C. (294 F.) to produce an optimum cure. The relative rates of aging of the vulcanized compositions were compared by measuring their respective tensile strength and elongations before and after aging.

Accelerated aging tests were carried out in the Geer aging oven, in which samples were maintained at a temperature of 70 0. (158 F.) in a constantly renewed stream of air, as well as in the Bierer-Davis bomb, in which other samples were maintained at the same temperature (70 C.) in an atmosphere of oxygen at a pressure of 300 lbs. per sq. in. The results of the tests are given in the table below, in which T indicates ultimate elongation in per cent. of original length.

Aging tests After 7 After 48 Before day in 3512 aging the Gcer Davis Anti-oxidant ove bomb T E T E T E None (control) 3520 G33 1920 453 753 297 p-nuphthylamino p-amino diphenyl methane 3710 637 2460 460 2060 495 Dinaplithyl diamino (liphenyl methane "I 3790 Example 2.-Another rubber composition was prepared and tested as indicated in Example 1 above, except that p-phenylamino tetraphenylmethane was employed as the anti-oxidant. The results of the tests are given in the following table:

Aging tests It is evident from the above examples that rubber compositions containing even small proportions of the anti-oxidants of this invention resist deterioration far more effectively than similar untreated compositions. Not only are they cutstandingly efficient antioxidants, but they do not discolor the rubber goods upon exposure to sunlight, as do all other known classes of effective age-resisters.

Obviously, the practice of this invention is not limited to the specific compositions given above, such compositions being merely illustrative of one manner of employing the anti-oxidants of this invention. The anti-oxidants may be employed in conjunction with other vulcanizing agents than those here specifically disclosed, for this invention is applicable generally to pure rubber or rubber compositions of the most varied nature. Certain of them, particularly the tetraaryl methane compounds, are exceptionally valuable for use in connection with the so-called acid cure because of their comparative inertness with respect to sulphur chloride.

It is to be understood that the term treating as employed in the appended claims is used in a generic sense to include either the incorporation of the anti-oxidants into the rubber by milling or similar process, or their addition to the rubber latex before the coagulation, or to the application thereof to the surface of a mass of crude or vulcanized rubber. The term ruber is likewise employed in the claims in a generic sense to include caoutchouc, whether natural or synthetic, reclaimed rubber, balata, gutta percha, rubber isomers and like products, whether or not admixed with fillers, pigments, vulcanizing or accelerating agents.

While I have herein disclosed certain preferred manners of performing my invention, I do not thereby desire or intend to limit myself solely thereto, for, as hitherto stated, the preci e proportions of the materials utilized may be varied and other materials having equivalent chemical properties may be employed if desired without departing from the spirit and scope of the invention, as defined in the appended claims.

This application is a division of my co-pending application Serial No. 521,010 filed March 7, 1931, which itself is a continuation of my co-pending application Serial No. 301,423 filed August 22, 1928.

I claim:

1. The process of vulcanizing rubber which comprises heating rubber a d sulfur in the presence of antioxidant comp sing a reaction product of an amino substituted triphenyl-methane and an aromatic hydrocarbon, wherein one or more hydrogen atoms thereof are substituted by hydroxyl groups only.

2. The process of vulcanizing rubber which comprisesheating rubber and sulfur in the presence of an antioxidant comprising a reaction product of a diamino substituted triphenylmethane and an aromatic hydrocarbon, wherein one or more hydrogen atoms thereof are substituted by hydroxyl groups only.

3. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an antioxidant comprising a reaction product of para-para-diamido-triphenyl-methane and an aromatic hydrocarbon, wherein one hydrogen atom is substituted by a hydroxyl group only.

4. The vulcanized rubber product prepared by heating rubber and sulfur in the presence of an antioxidant comprising a reaction product of an amino substituted triphenyl-methane and an aromatic hydrocarbon, wherein one or more hydrogen atoms thereof are substituted by hydroxyl groups only.

5. The vulcanized rubber product prepared by heating rubber and sulfur in the presence of an antioxidant comprising a reaction product of a diamino substituted triphenyhmethane and an aromatic hydrocarbon, wherein one or more hydrogen atoms thereof are substituted by hydroxyl groups only.

6. The vulcanized rubber product prepared by heating rubber and sulfur in the presence of an antioxidant comprising a reaction product of para-para-diamido-triphenyl-methane and an aromatic hydrocarbon, wherein one hydrocarbon atom is substituted by a hydroxyl group only.

7. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an antioxidant comprising a reaction product of an amino substituted triphenyl-methane and an aromatic hydrocarbon containing a single substituent, said substituent comprising a hydroxyl group.

8. The vulcanized rubber product prepared by heating rubber and sulfur in the presence of an antioxidant comprising a reaction product of an amino substituted triphenyl-methane and an aromatic hydrocarbon containing a single substituent, said substituent comprising a hydroxyl group.

9. The process of vulcanizing rubber which comprises heating rubber and sulfur in the presence of an antioxidant possessing the structural formula wherein R represents an aromatic hydrocarbon residue.

10. The vulcanized rubber product prepared by heating rubber and sulfur in the presence of an antioxidant possessing the structural formula N-R t wherein R represents an aromatic hydrocarbon residue.

11. The method of preserving rubber which comprises treating rubber with a triaryl-methane having at least two secondary amino groups substituted on different aryl groups.

12. The method of preserving rubber which comprises treating rubber with a secondary diamino triarylmethane.

13. The method of preserving rubber which comprises treating rubber with a di(arylamino) triarylmethane.

14. The method of preserving rubber which comprises treating rubber with diphenyl diamino triphenylmethane.

15. The method of preserving rubber which comprises treating rubber with a secondary triamino triphenylmethane.

16. The method of preserving rubber which comprises treating rubber with a tri(arylamino) triarylmethane.

17. The method of preserving rubber which comprises treating rubber with triphenyl triamino triphenyl methane.

18. A rubber composition comprising rubber and a triarylmethane having at least two arylamino groups substituted on different aryl groups.

19. A rubber composition comprising rubber and diphenyl diamino triphenylmethane.

20. A rubber composition comprising rubber and triphenyl triamino triphenylmethane.

ARTHUR W. SLOAN. 

